(1) Atomic radii : The atomic radii of noble gases increases on moving down the group and their atomic radii correspond to the vander Waal’s radii.

(2) Boiling points : The m.pt. and b.pt. increases from He to Rn, because of increase in magnitude of vander Waal’s forces.

(3) Polarizabiltiy : The polarizability increases down the group, He < Ne < Ar < Kr < Xe

(5) Heat of vaporization : They posses very low values of heat of vaporization, because of presence of very weak vander Waal’s forces of attraction between their monoatomic molecules. However the value of heat of vaporization increases with atomic number down the group and this shows that there is an increasing polarizability of the larger electronic clouds of the elements with higher atomic number.

(6) Solubility in water : They are slightly soluble in water. Their solubility generally increases with the increase in atomic number down the group.

(7) Adsorption by charcoal : All of them except helium are adsorbed by cocount charcoal at low temperature. The extent of adsorption increases down the group.

(8) Characteristic spectra : All of them give characteristic spectra, by which they can be identified.

(9) Liquification of gases : It is difficult to liquify noble gases as their atoms are held by weak vander Waal’s forces. Ease of liquification increases down the group from He to Rn. Helium has the lowest boiling point (4.18 K) of any known substance. The ease of liquification increases down the group due to increase in intermolecular forces.

The elements helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn), constitute zero group of the periodic table. These are gases at ordinary temperature and do not have chemical reactivity and therefore, these are called inert gases.